This invention relates to emergency evacuation equipment for aircraft, in particular, to inflatable aircraft evacuation slides.
The requirement for reliably evacuating airline passengers in the event of an emergency is well known. Emergencies at take-off and landing often demands swift removal of the passengers from the aircraft because of the potential of injuries from fire, explosion, or sinking in water. A conventional method of quickly evacuating a large number of passengers from an aircraft is to provide multiple emergency exits, each of which is equipped with an inflatable evacuation slide. These inflatable slides are normally stored in an uninflated condition in a container or packboard requiring a minimum of space in the interior of the aircraft and are typically either mounted on the interior of the aircraft door or immediately adjacent thereto. Opening of the aircraft emergency evacuation exit initiates the inflation of the emergency evacuation slide. The slide is rapidly inflated and ready for evacuation of passengers who in a very short period of time following opening of the exit. The descent of evacuees on an inflatable evacuation slide is primarily governed by the angle formed between the slide surface and the ground. The optimum rate is usually achieved when the angle they are between is from about 30xc2x0 at a minimum to about 50xc2x0 at a maximum. The lower the angle, the slower the rate of descent and the evacuation may not proceed with sufficient dispatch. If the angle is much greater than 50xc2x0, the slide surface may be too precipitous and evacuees may balk at descending the slide and/or may be injured upon impact with the ground.
Controlling the proper angle between the slide and ground is made more complex since the evacuation slides are normally utilized only in emergency situations. In such situations it may be that one or more of the landing gear of the aircraft have been damaged or collapsed such that the aircraft itself may be canted at a number of different possible angles. For example, if the nose landing gear collapses, the nose of the aircraft will drop and the fuselage will pivot about the main landing gear so that an escape exit located at the tail of the plane may be elevated substantially. An escape slide that is disposed at the proper angle for rapid but safe evacuation at a normal height would become too steep for safe evacuation from the elevated exits. Similarly, an escape slide that is disposed near the nose of the aircraft may be deployed at too shallow an angle for rapid evacuation.
Use of variable length evacuation slides has been suggested as a means to accommodate evacuation of passengers from an evacuation exit that may be elevated or depressed relative to the ground. U.S. Pat. No. 2,936,056 to Heyniger discloses an inflatable evacuation slide having an extensible portion held within a compartment closed by a zipper. If the evacuation slide is to be deployed in the long configuration, prior to inflation the zipper must be manually removed. Accordingly, whether to deploy the evacuation slide in the long configuration requires a manual act predicated on human judgement at a time of possible emotional stress.
U.S. Pat. No. 3,463,266 to Day discloses an extensible escape slide having inflatable side beams that are normally foreshortened in length but which may be extended when additional length is required. The determination as to whether to deploy the slide in the foreshortened or lengthened condition is made by dropping a weight attached to a predetermined length of cord. If the weight touches the ground, an electrical connection remains open and the extensible side beams are restrained in their foreshortened condition. If, however, the weight does not touch the ground, the weight closes a switch that releases a restraint allowing the side beams to deploy to their fullest extent.
Similarly, U.S. Pat. No. 3,544,344 to Summer, et al. discloses a variable length inflatable slide comprising a height sensing means consisting of a weight attached to a predetermined length of cable. Upon initiation of the evacuation slide, the weight is dropped. If the weight contacts the ground the cable is not activated to release the extensible portion and the slide deploys in its foreshortened condition. If, however, the mass does not contact the ground the weight draws a cone through a sleeve which locks the cable in a fixed position. As the slide deploys, the cable in its locked position releases the extensible portion under the force of the inflating slide.
As noted hereinbefore, evacuation slides having a manually deployed extension require human judgement at a time of possible emotional stress and therefore may be improperly deployed. Consequently these slides may be unreliable in service. Similarly, extensible escape slides that rely on the dropping of a plumb line to measure the distance from the slide to the ground are cumbersome and, because the weight and line may become fouled upon deployment, these designs also suffer from potential reliability problems. Accordingly, what is needed is an extensible emergency evacuation slide that does not rely on manual actuation or physical measurement of the distance to the ground to determine whether the slide is to be deployed in the foreshortened or extended configuration.
The present invention comprises an inflatable evacuation slide system including an evacuation slide that is selectively deployable in either a foreshortened or lengthened configuration based on the input from an electronic sensor. In an illustrative embodiment, the slide comprises a pair of main support tubes supporting a flexible slide surface. The foot end of the escape slide includes a compartment containing an extensible slide portion stored in an undeployed condition. The compartment is sealed by means of conventional speed lacing held together by a single master loop. A pyrotechnic cable cutter is attached to the master loop to sever it at the appropriate time, thereby releasing the extensible portion of the slide.
A control circuit determines whether to deploy the extensible portion based on input from a non-contacting electronic sensor such as an inclinometer. As noted hereinbefore, the principal reason for an egress opening to be elevated or depressed from its normal height during an emergency evacuation is that one or more of the aircraft landing gear has collapsed. The detection of a collapsed landing gear is translated to a deviation of the aircraft fuselage from its normal horizontal attitude into a nose down, tail down, port or starboard wing down attitude. Since the nose down, tail down, port or starboard wing down attitude can be detected electronically as a pitch and/or roll angle, a simple logic circuit can deploy each of the nose, over-wing and/or tail evacuation slides in the appropriate configuration reliably and without the use of cumbersome direct measurement techniques such as the dropping of a weight attached to a cable.